The present invention relates to a tool-mounting assembly which is composed of a basic tool holder equipped with a receiving pin and a tool head having a receiving bore corresponding to the receiving pin. The basic tool holder and the tool head are secured to each other by means of clamping elements. The clamping elements are actuated externally by means of a clamping screw so as to hold them in a position in which planar frontal faces which extend perpendicularly to a shaft axis and which surround the receiving pin of the basic tool holder as well as the receiving bore of the tool head lie against one another without play. Such tool devices permit, in particular, rapid exchange of the tool head, either manually or by machine.
European Patent Application EP-A1 No. 0,101,917 discloses a tool-mounting assembly whose coupling includes a chuck which extends coaxially to a pull rod and, when in the closed position, surrounds projections on the pull rod. The tool head is pulled via the pull rod, the chuck, and a pull shaft into a form-locking connection (Hirth-type serration) at the tool shaft. Although the Hirth-type serration does provide for positioning of the tool head without play, it has the drawback that it does not provide favorable securing means against the relatively high moments generated by the machining forces. As a result of the engagement angle of the individual teeth, axial deflection forces result from stress on the tool head and may adversely influence positioning. Moreover, the toothed coupling location is very susceptible to dirt. For the above-mentioned reasons, very high pulling forces must be generated as a whole and these are transferred via a tensioning sleeve to the clamping pin screwed into the tool head, thus highly stressing these parts.
It is also known to secure the tool head by means of balls which, upon movement of a pull rod, are able to drop into correspondingly shaped recesses. However, the balls exert a pressure at points on the contact faces of the recesses. Moreover, dirt in the recesses and the necessary high tensile stresses also result in considerable drawbacks here.